For your possible interest, here is a helpful article from the TidBITS Newsletter that addresses how to free up storage space in iCloud, Google, and Dropbox: https://tidbits.com/2020/02/17/how-to-deal-with-running-out-of-icloud-google-and-dropbox-space/
In particular, I found the section discussing iCloud storage to be quite informative and helpful, and addressed backup and storage issues that I wasn't aware of.
Jim Hamm